Re: [CAD_CAM_EDM_DRO] Re: Question on Power Supply

Polaraligned wrote:

>1.414 is the square root of 2, and is how we get the RMS value of
>a peak to peak voltage. The RMS value is also called the "effective
>voltage". Your 120vac household outlet is really 170v peak to peak.
>

(minute quibble here - it is 170 V peak (measuring from zero to EITHER
the positive or negatuve peak, thus 340 V Peak-to-Peak.)

>This RMS value is what most meters read.
>

And, most cheap meters take the peak voltage and then multiply by a
scaling factor
of 0.707 This works fine for true sine waves, but if the wave shape is
distorted, or
not at all sinusoidal (like square waves, pulses, etc.) the cheap meter
can give wildly
erroneous readings. For instance, the TRUE RMS value of a 120 V perfect
square
wave is 120 V. A cheap meter will tell you it is about 85 V! (120 V
peak * .707)
Worse, a narrow 120 V pulse will ALSO read about 85 V, although the true RMS
value would be, say, 12 V if it was a 10% duty cycle pulse, or 1.2 V for
a 1% pulse.
Way wrong! A true RMS meter will give the correct reading all these cases.

Jon